Improvement on the thermostability of electrostriction in Pb(Mg1/3Nb2/3)O3-PbTio3 relaxor system by La-doping

The thermostability of electrostriction in 0.9Pb(Mg1/3Nb2/3)O3-0.1PbTiO3 (0.9PMN-0.1PT) relaxor ferroelectric system was improved by enhancing the extent of the 1:1 short-range ordering in the B-site sublattice of perovskite structure. The enhanced short-range ordering was achieved by the partial substitution of La with Pb in the A-site. With increasing La content from 0 to 5 at.%, the diffuseness parameter (δ) increased from 43 K to 81 K, while TCE (temperature coefficient of electrostriction) decreased from 2.61% K-1 to 1.27% K-1. The product of TCE and δ exhibited a constant value regardless of the amount of La-doping, demonstrating that the enhanced 1:1 short-range ordering is directly related to the improvement on the thermostability of electrostriction. A semiempirical functional relationship between the electric field-related electrostrictive coefficient (M) and the polarization-related electrostrictive coefficient (Q) was derived. Based on this semiempirical relationship, practical guidelines on the selection of composition having an optimal thennostability ((∂/∂T)/M), together with a large field-induced strain, were suggested and discussed using the La-doped PMN-PT system as an example.

Keywords:

• Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃
• electrostrictive coefficient
• temperature coefficient of electrostriction (TCE)
• diffuseness parameter
• diffuse phase transition (DPT)
• short-range ordering